Film handling apparatus

ABSTRACT

Film handling apparatus has a continuously operated drive for passing the film through a film gate, and a tilting deflector which is moved in synchronism with the film during its forward tilt to compensate for the film motion in the film gate. Mechanical and electrical drives for the deflector are described as also are energy transfer means for bringing the mirror to an abrupt halt at the end of its return tilt motion.

United States Patent [191 Broeckl et al.

FILM HANDLING APPARATUS Assignees:

Karl Vockenhuber; Raimund Hauser, both of Vienna, Austria Filed:

Oct. 15, 1971 Appl. No.: 189,623

Foreign Application Priority Data Oct. 20, 1970 Nov. 5, 1970 Nov. 19,1970 Nov. 24, 1970 Mar. 4, 1971 Apr. 6, 1971 US. Cl. Int. Cl.

, A [45] Apr. 23, 1974 Primary Examiner-Monroe H. Hayes [5 7] ABSTRACTFilm handling apparatus has a continuously operated Austria 9455/70drive for passing the film through a film gate, and a i 9983/70 tiltingdeflector which is moved in synchronism with Austria 10457/70 the filmduring'its forward tilt to compensate for the A f 0601/70 film motion inthe film gate. Mechanical. and electrical 'f 1893/71 drives for thedeflector are described as also are en- Austria 2944/71 gy transfermeans for g g the mirror to an IIIIIIIIIIIIIIIIIIIIIIIIIIII 352/109abrupt halt at the end of its return tilt motion. G031) 41/10 2 Claims,30 Drawing Figures 30 57 a 29 54 35 9 7 K I- I E l a if EATENTEBAPRZS1974 3806244 SHEET 03 0F 11 FIG. I!

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SHEET 08 0F 11 Pmmmmes mu 3; 806; 24 4 swan 10 or 11 FIG-28 F7629 FILMHANDLING APPARATUS BACKGROUND OF THE INVENTION This invention relates tostrip handling apparatus such as a cine camera or projector, utilising astrip such as a film which is moved continuously through a gate. Moreparticularly the invention is concerned with details of an opticalsystem having a deflector which is driven to compensate for the motionof the strip with respect to the system when the apparatus is in use.The deflector with which the invention is concerned performs anoscillatory motion having a forward sweep motion during which it issynchronised with the strip movement through the gate, and a return orfly-back motion when the deflector is returned relatively rapidly to aninitial position in order to commence the next forward sweep.

Although the aspects of the invention mentioned below are primarilyconcerned with the photographic field, they may equally well findapplication in other fields, for example in the fields ofdata-recognition or computors.

SUMMARY OF THE INVENTION movement of the film through the film gate, thedeflecting drive producing a forward motion of the deflector to followmovement of the film and a comparatively rapid return motion, anarrangement for synchronizing the deflecting drive with the film drive,and energy transfer means for halting in recoilless manner thedefleeting drive at the end of the return motion such means transferringfrom the drive a quantity of energy which is substantially equal to thedynamic energy of said deflector on reaching said end.

An advantage of this aspect of the invention is that on completion ofits fly-back motion the deflector is brought substantiallyinstantaneously, and without recoil, from its maximum fly-back velocityto rest at the position from which it is to execute its next forwardsweep. This would not be possible were resistive braking to be used asit would require careful control and a finite time in which to act. Theenergy transfer means may operate in one of two ways. In the preferredarrangement cancellation of the dynamic energy of the deflector isachieved substantially instantaneously by injecting into its drive anelectrical signal having an equal and opposite energy content. This maybe achieved with a galvanometer type deflector drive, by injecting intothe galvanometer an impulse of predetermined shape. This shape ispreferably combined with an electrical impulse required to sweep thedeflector forwardly in synchronism'with the film or strip and the twoimpulses are suitably provided by a double impulse generator operated insynchronism with the drive for the film.

In an alternative arrangement the energy transfer means transfer thedynamic energy of the deflector drive to a buffer whose motion can besubsequently halted when separated by the impact from the deflectordrive. In such an arrangement the mass of the buffer is matched to thatof the deflector so that with impact of the latter on the former thedeflector dynamic energy is transferred in toto to the buffer and itsreturn motion is in this way brought to an abrupt halt. The buffer ismeanwhile jolted into motion by the impact and its energy can bedissipated thereafter in any convenient way without influencing thedeflector drive.

In accordance with a second aspect of the invention there is providedstrip handling apparatus having an arrangement composed of an objectivelens unit disposed between a picture window in a gate and a tilt-mirror,such arrangement optically adjusting the moving image position of aguided perforated strip, the tilt-mirror being rockable about an axisunder the control of a scanning mechanism which includes a clawpositionally controlled by a perforation of the strip when engagedtherewith and mounted on an arm so as to move arcuately about a radiuswhich, allowing for a i 5 percent tolerance, is twice the distance ofthe window from the lens unit.

In accordancewith a third aspect of the invention there is provided filmhandling apparatus with an arrangement formed with a tilt-mirror tocompensate optically for movement of the image picture of a perforatedstrip guided around an optically smooth partcylindrical surface, thetilt-mirror being driven to turn about an axis provided by a torsion barhaving at one end a first fixture holding the torsion bar endstationary, intermediate its ends a second attachment fixture on whichthe tilt-mirror is mounted, and at its second end the torsion bar isprovided with a third fixture to which is attached a mechanism whicharcuately moves the mirror by engaging a perforation of the perforatedstrip while travelling around the cylindrical surface which is centredon the axis of the torsion bar. I

In accordance with a fourth aspect of the invention there is providedstrip handling apparatus having a single tiltable optical deflector tofollow motion of a moving strip and which is driven through a drivecoupling having two couplers which operate in succession to each producea relatively slow forward follow motion of the deflector, each couplerbeing decoupled from the mirror on completion of the slow forward motionand a further driven then returning the deflector rapidly to its initialposition where it is engaged by the second coupler to execute asecondforward motion during which the first coupler returns to itsinitialposition.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 6 is an electrical block circuitshowing control circuitry for a tilt-mirror drive motor;

FIG. 7 isa block circuit showing another way of synchronizingelectrically the control of the tilt-mirror drive; I FIG. 8 showsdiagrammatically a further. way of electrically controlling thetilt-mirror drive;

FIG. 9 shows a way of extracting a synchronizing impulse from a filmperforation;

FIG. 10 represents a preferred arrangement of impulse generatoremploying an information carrier;

FIG. 11 shows diagrammatically signals obtained from respectively fourtracks recorded on an information carrier;

FIG. 12 shows an alternative arrangement of information carrier to thatshown in FIG. 10;

FIG. 13 shows how an impulse may be divided between two differentrecording tracks;

FIG. 14 shows diagrammatically a centrifugal governor for controllingvariable electrical resistances employed in the arrangements shown inFIGS. 9 to 11;

FIG. 15 shows diagrammatically a further way of producing electricalimpulses for controlling movement of a tilt-mirror, or other form ofoptical deflector and synchronised with the movement of a film strip;

FIG. 16 shows schematically a further arrangement using a telecenteringdevice and a claw arm for maintaining synchronous movement between afilm strip and a tilt-mirror;

FIG. 17 shows diagrammatically an electrical waveform supplied to aballistic galvanometer drive for a tilt-mirror;

FIG. 18 shows an arrangement for scanning a film strip and which insteadof using telecentering as in FIG. 16, uses a film gate having a zone ofincreased'curvature;

FIG. 19 shows in block diagrammatic form a circuit for triggeringrelease of a double impulse from a magnetic field dependent resistor;

FIG. 20 shows diagramatically, and with the help of a block circuitdiagram, an arrangement for synchronizing motion of a tilt-mirrordeflector with the movement of a film through a film gate;

FIG. '21 shows an arrangement for terminating flyback motion of atilt-mirror in a recoilless manner and without mechanical breaking;

FIGS. 22 and 23 respectively show modifications of the recoillessarrangement of FIG. 21;

FIGS. 24 and 25 show diagrammatically in respectively side and end viewsan arrangement for maintaining the angular movement of a tilt-mirror tohalf that of a claw arm by means of a torsion bar; FIG. 25 being takenin the direction of the arrow XXV in FIG. 24;

FIGS. 26 and 27 respectively show in side and plan views a cam-drivenarrangement for maintaining forward tilt motion of a mirror deflector instep with DESCRIPTION OF PREFERRED EMBODIMENTS In the apparatus of theinvention, the individual film frames are projected by means of aswivel-mounted tilting mirror and a projector objective assembly. Themirror is so moved that motion of the film is compensated and astationary picture is formed on the projector screen or framed in thecamera window. A special arrangement produces electrical impulses fromoptical markings on the film, for example from the perforations, andthese impulses control with the film movement the synchronous movementof the mirror. The electrical control of position results in such a waythat extremely short fly-back times for the mirror achieved without thepresence of other moving parts in the optical path, in FIGS. 1 to 20.

FIG. I shows a film strip 1 which is continuously moved by known meansacross a film gate 2 having a window 3 and associated with two rollsorguide, pins 4 provided for properly positioning the film on the filmgate; A light source, comprising a lamp 5, mirror 6 and condensing lens7, illuminates as evenly as possible the window 3 which is filled by twopicture frames of the film strip.The brightness information arrivingfrom the film 1 and window 2 encounters the tilting-mirror 8 positionedby the spindle of a tilt motor 9 and is transmitted through an objectiveassembly 10 to the projector screen or similar surface. Thesynchronisation of the film movement with the mirror movement necessaryfor faultless presentation of the film, is achieved with a synchronizingarrangement consisting of a lamp 12, an optical system 13 and a lightreceiver 14. The light from the lamp 12 reflected from the film istransmitted through the optical system 13 to the receiver 14 whichconverts the light into electrical current. The arrival of a perforationor a non-reflecting zone of the film margin in the optical path,produces an electrical pulse in the receiver output, which is amplifiedby amplifiers 15 and 16 and used to control the positioning of thetiltmirror 8. In order to make adjustment of the picture frame linepossible, the entire assembly comprising the parts 12, 13 and 4 isdisplaceable longitudinally of the film.

In FIG. 2 is shown another driving system of a tiltingmirror. The lightfrom a projector lamp (not shown) is transmitted as before through thewindow 3 of a film gate 2 onto a movably mounted tiltable-mirror 8 whichreflects the light through the objective assembly 10 onto ascreen 11.The mirror is movably mounted with the help of a woven or plastics strip17 and is tiltable against an angle stop 18. A reciprocating pulsedsystem, similar to a dynamic loudspeaker, drives the free end of themirror with the help of a lacquer stiffened woven or plastics strip 19.In this way linear motion is converted into a tilting motion of themirror. The diaphragm arrangementnecessary for centering the magneticcoil does, however, impart a dynamic couple to the surrounding air sothat an oscillatory drive of this design for the mirror developes morenoise than a motor constructed on the principle of a galvanometer.

FIG. 3 shows one possible arrangement of such a galvanometer motor.Located between poles of a magnet 20 are a static iron core 21 and aspindle 22 on which a coil 23 is rotatably mounted, the spindle beingheld in its initial position by a spring 24. A damping liquid 25provides damping. It can also be advantageous to utilise copper oraluminium frames to produce damping by eddy-current effect. Liquiddamping has, however, the advantage that the liquid enables lowernatural resonance frequencies of the oscillatory system to be damped sothat a more sensitive motor can be used.

In FIG. 4 is shown a motor which is provided with a known deflectingarrangement. The coil is mounted on a torsion strip 26, whosecross-section is so chosen that it readily permits torsionaloscillations while preventing oscillations normal to the torsional axis.A suitable profile for the torsion spring is one of generally cruciformcross-section.

FIG. 5 shows a possible current waveform through the oscillatory coil ofthe motor enabling on extremely short fly-back time to be achieved.During the time T,, a reverse current impulse of magnitude U,, isgenerated, the impulse being triggered from the synchronizing signal ofthe film and accelerating the oscillatory coil and thus the mirror veryrapidly to its initial position. Were only this reverse impulse to beimpressed on the oscillatory system, the oscillatory coil after itsoperation would move beyond the initial position and begin to execute adamped oscillation that would be useless for the intended operation.Therefore a braking pulse is applied for a suitable time T to theoscillatory system as a continuation of the reverse pulse and has amagnitude U the braking pulse halting the oscillatory coil at the end ofthe time T The oscillatory coil is still when a further sawtoothwaveform current beings the deflec tion of the mirror over a period T;,.As the current at the beginning of the sawtooth is identical with thecurrent at the end of the braking impulse, a current buildup process isaccordingly avoided and the mirror executes an exact tilting motion.With such an arrangement fly-back times in the region of half amillisecond are obtainable.

In FIG. 6 is shown a block diagram of the electrical circuit of themotor. The synchronizing impulse from the film perforation enters theamplifier at 28. The amplifier 15 drives a sawtooth generator 29 whichhas amplitude and linearity regulators 30 and 31, respectively, and alsoa double impulse generator 32 having controls 32 and 33 for regulatingthe times T, and T The sawtooth waveform and the double impulse areadded to one another in a mixing circuit 34 to obtain the waveform ofthe shape shown in FIG. 5, which controls by way of an output stage 35the motor 9. The frequency of the sawtooth generator 29 can be matchedto different film velocities.

FIG. 7, like FIG. 6, shows in block diagrammatic form, a motor controlcircuit providing indirect synchronisation. The frequency of anoscillator 36 is compared in a phase comparator 37 with a synchronizingimpulse and a regulating voltage produced by the comparator so controlsthe oscillator 36 that the frequency and phase of the oscillator outputand the synchronizing impulses coincides.

FIG. 8 shows another possible arrangement for the mirror-tiltingmechanism. The synchronizing marks on the film border are imaged bymeans of an optical system consisting of illuminating components 5 to 7,the tilt-mirror 8 and the objective 10, on two light detectors such asphoto-cells 39 and 40. With the assistance of a differential amplifier41, the motor 9 is now so controlled that the image of the synchronizingm'ark always falls evenly on both photo-cells. Departure of thesynchronizing mark from the window 3, produces in the amplifier 41 apulse which controls the rapid return motion of the mirror to itsstarting position. In the case of an unbiased mirror-tilting motor 9,the existing rectangular double impulse from the generator 38,. Oh-

tained as before, is fed to the mixer 34 which supplies the output stage35 controlling the motor 9.

' FIG. 9 shows a possible arrangement of generating impulses from theperforations and which is also usable with a flank film.

The film 1 travels between two electrodes which are constructed as acondenser.

As a result of the change in dielectric strength in the presence of aperforation, the capacity of the condenser changes. As this condenserforms part of a resonant circuit of an oscillator 43, an impulse forcontrolling the motor 9 can be generated by a frequency discriminatorconnected to the oscillator 43 each time the oscillator frequencyassumes a value significant of the presence of a perforation between thecondenser electrodes. One can also so arrange the oscillator 43 that itonly oscillates to generate a control pulse for the motor 9 when aperforation lies between the electrodes of the condenser 42.

According to FIG. 10 there is provided an information carrier,constructed as a disc 45, for a synchronous production of the desiredimpulses. The disc is driven by a sprocket wheel 46 whose teeth 47engages in the film perforations.

The impulses are represented on the disc 45 as cutouts 48,49 provided ina control track on the margin of the disc. These cut-outs areilluminated by a schematically depicted projection system having a smalllamp and a lens 51, in such a way that light from the projection systemfalls on a photoelectric transducer 52. The

transducer deliversa stronger or weaker output signal which variescontinuously with the strength of the light allowed through the cut-outs48,49. In the case of the sawtooth-signal-forming cut-out 48, the outputsignal of the transducer 52 will also exhibit a sawtooth developmentand, after the attainment of a certain level will fall suddenly again tozero so that, a galvanometer constructed as in FIG. 3, for example, isreturned to an initial position under the action of the force of arestoring spring 24. In order to prevent a swing of the galvanometercoil frame 23 in this case, a braking impulse is supplied subsequentlyto the frame by means of the cut-out 49. The described arrangement givesrise to the advantage that the control track formed by the cut-outs48,49 is not subjected to wear. In the case of a magnetic recordingcontrol track or the employment of a sound groove, it is preferable ifseveral information tracks of thesame kind are provided whereby theappropriate track-reading device can be switched from one track to thenext, should track wear make it necessary. v

FIG. 1 1 illustrates another arrangement in which four different controltracks are provided on an information carrier not shown in detail.Sawtooth waves are recorded on the track 53, which serve as the tiltcontrol of the mirror 8 with forward movement of the strip,

whereas the track 54 contains oppositely directed sawteeth for enablingprojection to occur during reverse running of the film. The doubleimpulses which are provided in the track 55 are supplied to the electricmotor oscillatory system either directly, for example by means of asecond galvanometer coil winding, or indirectly, by way of a mixingstage. The sawtooth signal 56 finally serves for synchronisation of asound recording and extends preferably over more than the illustratedimpulse s,'for example over a span of 16 impulses.

In FIG. 12 a disc 57, arranged in much the same way as the disc 45, isformed with recorded tracks 53- 55, which in the illustrated embodimentare read by means of magnetic pick-up heads 58-60. This results inaccordingly simple switching from the track 53 to the track 54 by reasonof thefact that a control switch 61 has two contacts 62, 63 respectivelyarranged in the current circuits of the magnetic heads 59, 60 and whichoperate in reverse senses so that when it is open the other is closed.In this way mechanical displacement of the read-out arrangement from onetrack to another is avoided.

It is advantageous from a practical viewpoint, especially with opticalscanning of a record formed on a data carrier, if there is present inthe track 64 (see FIG. 13) the impulse effective in one direction, thatis to say to have recorded thereon the sawtooth as well as the brakingimpulse, whereas the fly-back impulse is in the track 65 and iseffective in the reverse direction. In that case a positive impulse ofcombined signals is supplied by the track 64 and the track 65 supplies anegative impulse of combined signals.

In addition to the employment of frequencymodulated recordings on acarrier, there is provided for the arrangements, such are as illustratedin FIGS. 6-8, a regulator controlling the amplitude of the doubleimpulse generator in accordance with the film velocity and also, if theoccasion arises, the amplitude of the sawtooth generator 29 byadjustment of the resistances of the regulators 32, 33 and 30, 31,respectively. In this case these resistances can be constructed ascentrifugally controlled resistors as may be visualised from theschematically shown arrangement in FIG. 14 where a centrifugal governorcontrols the tapping points of the two resistors disposed ondiametrically opposite sides beneath the governor.

A'further form ofcontrolfor use with the invention is illustrated inFIG. 15. 'In this case a lamp is again provided for illuminating theperforation ofa film strip 1, whereby the image of the perforation isprojected onto a generally rectangular photo-electric transducer 67 bymeans of a schematically indicated optic 1 0 and a screen 66 formed witha slit. A vignetting mask 68 is disposed between the screen 66 and thetransducer 67 and is formed with a triangular slot 69 which limits thelength of the slit image projected onto the transducer 67, in accordancewith the position at which the image appears. During the movement of thefilm 1 over a film gate (not shown), the projected images of the slit inthe screen 66travel in corresponding manner over the vignetting mask 68,the transmitted slit images maintaining lengths corresponding to thebreadths of the triangular slot 69 and producing from the transducer 67a larger or smaller output signal.that possesses a sawtooth wave shapeas a consequence of the triangular slot 69. The sawtooth, so formed isled through a threshold limiting switching circuit 70, for example aSchmidt-Trigger, which triggers operation of a double impulse generator38 on one side and-extends on the Within the scope of the invention manydifferentv construetions are imaginable. For example it is possible torecord an impulse, shaped as shown in FIG. 5, from the outset directlyonto a pilot track on the film. In a system not requiring a fly-backforce, the sawtooth can also have zero gradient i.e. have the samecurrent magnitude. Such a system is illustrated in FIG. 16 where partshaving the same function as corresponding parts in Figures alreadydescribed, bear the same reference numerals. Here also, the film 1 ispulled across the film gate 2 containing the windows 3 at a uniformspeed. The drive is obtained from a drive roll A which cooperates with aroller 4. Remote from the window 3, the film gate is additionally formedwith another o'pening or slit 3a in which the toe of a film feed claw 73can engage. The film feed claw 73 is supported on a claw arm 72 and ispressed by an angle spring 74 towards the film 1 and its perforations,respectively. The claw arm 72 is attached to the coil 23 of thegalvanometer 9 on the pivot 22 of which the mirror 8 is fastened bymeans of a holder 76 and a clamping screw 71.

The galvanometer is suitably constructed without a restoring bias andits film-following motion is controlled by the claw 73. To this end itcontinuously receives from the double impulse generator a voltage U;,,see FIG. 17.'The voltage U ensures that the claw 73 is not dragged fromthe perforation of the film momentarily engaged, as formerly commonlyoccurred. On the contrary, the leading end of the claw 73 lies againstthe leading edge of the momentarily engaged perforation, looking in thedirection of movement of the film, instead of being pulled as formerly.The thrust of the claw 73 is naturally very small indeed and is onlyjust sufficient to hold the leading end of the claw 73 in position atthe forward end of the engaged perforation. It is thus assured that theside of the momentarily-engaged perforation engaged in the projector isthe same side-as that engaged by the filmdrive claw in the camera. Inthis way tolerances in the spacing of the perforations do not affect thepositioning of the mirror.

At the end of the movement of the claw 73 and claw arm 72 synchronisedwith the film speed, a lug 77 nevertheless it is clear that these partsare arranged across the path of the lug 77. The arrangeent of the vlight path assembly is not essential to the invention.

- As well as the arrangement where thelamp 78 is arranged on one side ofthe lug 77 and the device 79 is arranged on the other, one can alsoarrange for the lamp 78 and device 79 to lie on the same side of the lug77, in this case the device 79 receiving light by way of a mirrorformed, for example, by a reflecting surface on the lug 77. In each casea change in the output of the device 79 is produced by the lug 77 in thebeaminterception position, whereupon fly-back impulse with a voltage U,and braking impulse with the voltage U, are released by a switchingstage 8. As is obvious, when the claw 73 is constructed as a pawl with'a slanting trailing surface, it does not require an additionalarrangement in order to reposition the galvanometer coil 23 and the clawarm 72 and extract the claw 73 from the perforation. his clear that themoment of the claw arm 72 on the coil pivot 23 should be compensated,Also the galvanometer 9 is correspondingly damped, for example byutilising a short-circuited coil and/or by designing the amplifier 35vwith a very small output impedance. To attain an effective electricaldamping a sufficiently strong magnetic excitation of the galvanometer isnecessary. For example, the field strengths in question should approacharound 5000 gauss.

A further problem with utilising a claw lies in the fact that, with itsangular movement, for example corresponding to one frame on the filml,the mirror 8 although mounted on the same axis, is required to movethrough only half the angle of the claw arm 72 as the angle between theincident and reflected beam on the mirror is doubled. This problem maybe solved in different ways.

In the example illustrated schematically in FIG. 16,

the mirror 8 is part of an optical system having a forward lens group 10and a rear lens group 10a. This optical system produces a telecenteringeffect on the light path, whereby the mirror 8 is arranged approximatelyin the zone of highest concentration of the light beams from the lens 10so that it can be made very small.

The object distance g between the forward lens group 10 and the picturewindow 3 corresponds in the illustrated example to the focal length ofthe lens group 10, so that a parallel beam of light is produced behindthe I lens group 10. An exceptional freedom from distortion is achievedby the utilisation of the set forth optical system, enabling the mirror'8'to be extremely small. The radius r of the claw arm 72 with the claw73 is now dimensioned, according to a development of the invention, tobe twice as large as the focal length of the lens group 10. In this waynot only is the solution to the above-mentioned problem found, namely amechanically-free ratio between the movement of the claw with the radiusr and the movement of a film frame with the effective optical radiuscorresponding to the focal length g but besides one also has a greaterfreedom regarding the disposition of the slit 3a in the film gate. Thedimension of the radius r corresponding to twice the focal length g canexhibit tolerances of :t 10 percent. With the use of a telecentered beampaths in the illustrated manner, there is achieved in addition tonegligible aberration a reduction in the importance of the tolerances toan insignificant level.

As is known, standards govern the spacing between the claw operatingslit and the film gate of a camera. For example, in accordance with oneof these standards the claw slit'should lie between two and threeperforation ahead of the picture window. These regulations can beapplied in corresponding manner to the apparatus of the invention bydesigning the length of the claw arm 72 in the described way. It is thusa question of a projector having the advantage that the claw 73 actuallyoccupies the same position which the claw in the camera occupied. Also,by this means, a greater precision in the guiding movement of the mirroris achieved.

As mentioned, the galvanometer is advantageously constructed without arestoring bias. It is clear from the above description, that the clawarm 72 is not required to apply any mechanical force. For this reasonthe claw arm 72 may be formed as a slender needle. Its mass is thereforeextremely small. If desired, it is also readily possible to apply abiasing force in one or other direction. This biasing force operates,referring to the galvanometer in FIG. 16 in the clockwise sense, so thatit is necessary to apply to the galvanometer a sawtooth voltage inplace. of the constant voltage U On the other hand, if the biasing,force is applied in the counterclockwise direction, the voltage appliedin the time t, (FIG. 17) can be reduced. In circumstances when themechanical biasing force is of the same magnitude over the entireangular range of movement of the claw it is sufficient to reduce theapplied voltage in the time t, to

- zero but if the mechanical restoring bias has a varying magnitude, thevoltage in the time can be correspondingly shaped, for example, as anoppositely directed sawtoothto the sawtooth illustrated in FIG. 5. Thetime intervals t ,t shown inFIG. 17 correspond to the time intervalsT,,'T in FIG. 5.

' The above-described dimensioning of the length of the claw arm 72 maybe also applied to another optical system which does not employtelecentered optical paths, as is shown in FIG. 18. To avoid greaterdistortion, it is advisable to give the film gate 2 a double curvature,namely in the region of the picture window 3 a curvature with theoptical radius R, whereas. in the regions adjacent to the picture window3 and/or in the region of the slit for the claw insertion (3a in FIG.1), a curvature approximating to the radius r of the claw arm 72, It isalso evident from FIG. 18 that the mirror 8 must be made, substantiallylarger when employing an optical system without telecenteredopticalpaths.

It is not necessary to use the light assembly shown in FIG. 16 in orderto triggerrelea'se of the double impulse when the claw 75 reaches itsterminal position. In

' the case in question a solution by means of contacts is possible. Amagnetic field dependent resistor 81 (FIG. 19) can be provided on themovable part of the galvanometer 9 inside the magnetic field, theresistor triggering the release of th'e double impulses by way of aswitching stage. With the circuitry shown in FIG. 19 a steady voltagecorresponding to the voltage U, is supplied to a mixing stage 34, ontowhich, in this case, is

rangements are also conceivable. It is, for example, I

possible also to scan the film perforations in an optical light beam.Such scanning is conceivable for copies in which, asis generally thecase, the filmin the region of the perforation is transparent as evenatransparent film will absorb a portion of the light passing through it.Furthermore a portion of the light beam incident on the film isreflected back. By means of both of: these effects, namely absorbtio nand reflection, is the detection of the perforation possible. 7

A further possibility is illustrated in FIG. 20. The arrangement shownis in this case similar to that of FIGS. 1 and 6. Here also, light froma lamp 5 is projected by way of a condenser 7, the picture window andthe tiltmirror 8 onto a screen 11a of, for example, a television tube.Conforming likewise to the block diagram of FIG. 6, are an amplifier 15,a saw-tooth generator 29 with resistor 31 for amplitude adjustment, amixing stage 34, output amplifier 35 and double impulse generator 38. Inthe illustrated example of FIG. 20, however, the synchronizing controlis to the same extent modified as a semi-reflecting sheet 82 isadditionally provided in between the tilt-mirror 8 and the screen 11a,to direct light through an objective 87 and a screen 88 with arectangular opening onto a flat sensitive surface of a photo diode 89.The screen 88 has its opening so constructed that, during projection,the picture of the perforation falls partially on the screen 88 andpartially through its opening onto the photo diode 89. When the motionof the picture past the tilt-mirror 8 is correctly compensated, aconstant voltage to the arrangement is provided at the output of photodiode 89. Every error in the optical compensation is detected by adecrease or increase, respectively, in the signal output voltage of thephoto diode with reference to the desired voltage.

The output signal from the photo diode 89 is then processed in adifferential amplifier 90 which receives a reference voltage from afurther photo-electric transducer 91 illuminated directly by the lamp 5.If the scanning of the picture is error-free, the differential amplifier90 delivers a standard voltage of value 0. In either case, however, theoutput of the amplifier 90 becomes greater or smaller, a positive ornegative control voltage is made available which is supplied to thesawtoothgenerator 29 and used to control the steepness of the sawtooth.Should, therefore, the former steepness setting of the'sawtoothgenerator not precisely agree, such setting is brought back to theoptimum value by means of the illustrated control circuit. Moreover,synchronous oscillations of the film can also be compensated by thiscontrol circuit;

lnthe arrangement of FIG. 21 the film 1 is led along an arcuately curvedpath by means of a film gate (not shown). The film is continuouslydriven by means of a driving arrangement exemplified by a capstan A witha pressure roller 4.

The tilt-mirror 8, rockable about the axis 22, is disposed in thegeometric centre of the arcuately curved path and in the path of a lightbeam from the light producing assembly 5,7. A film picture is projectedby the light generating assembly 5,7 onto a conjugate flat sur-' face 11with the help of the tilt-mirror 8 which follows the movement of thefilm picture. The details of the projection arrangement not essential tothe invention are only schematically depicted.

Thedrive for the tilt-mirror is obtained from an arm 72 connected to themirror 8 and rockable around the axis 22, a known drag-elaw 110 beingcarried by the arm 72. The drag claw locates in the perforation of thefilm and participates in its movement once for each frame of the film.The drag claw is turnable about an axis 111 and is held by a spring 112in a position at which it engages a stop 113. At the end of theparticipating movement of the drag claw 110 and the arm 72, a fixed stop72 pushes in the leading face of a limb of the drag claw 110 against theweak thrust of the spring 112, whereby the claw is extracted from thefilm perforation. The arm 72 then returns quickly to its originalposition under the action of the spring which, referring to FIG. 1,gives the arm 72 a turning movement in the clockwise direction.

At the end of its returning movement the mass of the arm 72 and all themasses attached to it must be braked. This is the more critical as thefly-back time ought to be kept very short and also high velocitiesoccur. The braking occurs, in accordance with the embodiment of theinvention, through the use of a buffer 115 whose mass related ,to theimpact point P. between the arm 72 and the buffer I15 is selected toequal the magnitude of the mass of the arm 72 and the masses connectedto it. Thus at the end of its motion the arm 72 strikes against thebuffer so that the arm 72 is brought to a standstill and the entireenergy of the arm 72 is transferred to the buffer 115 where it isabsorbed by a spring 116. The buffer 115 is subsequently moved by thespring 116 back towards a cushioning stop 117. There is sufficient timewith the arrangement for the return motion of the buffer 1 because thearm 72 has in the meantime recommenced its correspondingly slow forwardmovement.

In order to prevent unwanted turning moments occurring with the impactof both masses, it is advantageous if the impact point P liessubstantially on a line b which connects the centres of inertia M and Sof the arm 72 and the buffer 115 respectively to one another. The entiremass of the arm 72 together with the masses trated at the centre ofinertia M, and the same is valid for the centre of inertia S of thebuffer 115. In the embodiment of the invention shown in FIG. 21 theabove advantage is realised by the buffer 115 being attached to an arm118 which turns about the same shaft 22 as the arm 72. In such aconstruction'it is under some circumstances advantageous for the pivotshafts of the arm 72 and the buffer 115 to be structurally separate fromone another, however in axial alignment.

The invention is however in no way limited to the illustratedarrangement of buffer. It is sufficient,for instance, that the locationof the impact point A is arranged where the path of movement of thebuffer 115 is tangential to the arc with the radius of gyration of thearm 72.

FIGS. 22 and 23 explain in detail examples of such an arrangement. InFIG. 22 an arcuate path b is pro. vided forthe buffer 115a which has acentre of inertia S and which isattached to an arm 118a so as to beswingable about a pivot point W. On the other hand the centre of inertiaof the claw arm 72 swings along an arcuate path b". As is apparent, thearcuate paths meet one another tangentially.

The-pivot point W need'not necessarily be arranged in theillustratedmanner. It could, for example, also lie in the region of thepivot shaft 22 to result in a very flat intersection of the arcuatepaths b and b", respectively. I v a y In the illustrated examples ofFIGS. 21 and 22, the masses of the buffers 115 and 115a, respectively,as referred to the impact point P are determined from the formula forcalculation of a moment of inertia:

where J is the moment of inertia, m is the mass of the buffer, and r isthe distance of the centre of inertia from its axis of rotation. As alsothemass referred to the impact point'P depends on the radius r, the massm can be kept proportionately small. As FIG. 23 shows, this ishowevernot an essential prerequisite for the invention. In accordancewith FIG. 23 thecentre of inertia M of the arm 72 again follows anarcuate path b", whereas the buffer 115b is guided linearly so that itscentre of inertia coincides with its centre of gravity and follows alinear path s. The arrangement of FIG. 23 could also be carried out inthe reverse manner, in that the mass connected with the mirror 8 isguided linearly connected to it can be thought of as lumps concenvmirror 8 in the centre of its curvature'require special 7 measures inorder to ensure that, with progression of the film through one filmframe, the deviation of the mirror 8 corresponds solely to a half filmframe. These requirements stem from the known doubling of the angledefined between the incident and reflected light rays and referred tothe tilting angle of the mirror. It is also apparent from FIGS. 24 and25 that one can forego a special spring for the fly-back of the claw arm72 if the shaft 22 is formed by a torsion bar which has one end fixedand the arm 72 clamped to the other end while the mirror 8 is attachedto the centre. In this case the torsional movement at the centre of thetorsion bar amounts to precisely half the torsional movement at theclamping point of the arm 72. Possible inaccuracies can be adjusted outby displacement of one of the fixtrues, preferably the claw arm clampingfixture.

FIG. 25 explains how the'individual parts are connected to the torsionbar 22. The torsion bar22 is fixed by means of a grub screw 215 in apedestal 216. The

pedestal is slidable lengthwise of the axis of the torsion bar 22 insidea slot provided in a base plate 217 and is positionally fixed by meansof a bolt 218.'The attachment point-for the grub screw 215 can bedisplaced along the axis of the torsion bar 22 by sliding thepedestal.216 after'the screw 215 and bolt 218 have been slackened.

The claw arm 72 is attached to the other end of the torsion bar. The arm72 can also be displaced along the axis of the torsion bar 22 to makeadjustments, after loosening of its clamping screw 119.

As is shown, the spacing between the attachment points of the screws 215and 119 is 2a. In the illustrated example, the mirror is fixed adistance a from the attachment points of the screws 215 and 1l9,respectively, by means of a clamp 120 having a clamping screw 121 sothat the mirror is also fixed in the middle of the torsion bar 22. Asthe torsion'bar 22 is fixedly held at one end in the pedestal 216whereas its end to which the claw arm 72 is attached participates in atorsional movement corresponding to the turning movement of the arm 72,the torsional movement in the middle of the torsion bar 22 is exactlyhalf. In this way an angular movement of the arm -72 amounting to anangle a is transmitted to the mirror in the ratio a. In this manner notonly is the desired reduction of the arms movement, and also, if theoccasion arises, by shifting the arm 72 lengthwise of the axis of thetorsion bar 22.

Referring to FIG. 26 and 27 a shaft 301 is provided on a small filmprojector whose individual parts are not illustrated, the shaft carryinga sprocket wheel 302 constructed in conventional manner. Furthermore atiltmirror 303 is pivoted for swinging movement about airs 551; 304,305. Thetilt-ini r ror 303 isbias edin a counterclockwise direction (seeFIG. 26) by an angle spring 306 shown in FIG. 27. The axle pins 304, 305project into support bores provided in support cheeks 307, 308. In thisway the mirror is lightly pivotally turnable and possesses a small mass.

Two sensing levers 309, 310 are pivotted on the axle pin 304, which bymeans of cam followers 311, 312 ride on respective cams 313, 314attached to the shaft 301. Consequently the sensing levers 309, 310perform oscillatory movements around the axle pin 304 while followingthe camming profiles of the cams 313, 314. FIG. 28 shows the arrangementof the sensing levers 309, 310 in exploded form. It is apparent that thecamming profiles of the cams 313, 314 are angularly displaced about halfa cam projection with respect to one another.

Two pawl carriers 315, 316 are pivoted to the axle. pin 303 and operatebetween the tilt-mirror 303 and the sensing levers 309, 310. As isclearly shown in FIGS. 26 and 28 the axle pin 304 passes in this casethrough elongated slots 317, 318 formed in both pawl carriers. The pawlcarriers 315, 316 are biased on the one hand by tension springs 319,320and are braced on the other hand by extensions 321, 322 which rest onstuds 323 and 324, respectively, provided on the sensing levers 309,310.In this waythe force of the bias springs 319, 320 is not only exerted byway of the extensions 321, 322 and the studs 323, 324 on the sensinglevers 309, 310 whereby it is assured that the cam followers 311, 312follow the cams 313, 314, but also the pawl carriers 315, 316, whichslide easily within limited ranges of movement determined by theelongation clockwise direction during which it slowly turns the tilt--mirror 303 by way of the associated pawl. At the end of this movementthe pawl becomes disengaged to allow the mirror 303 to return quickly toits initial position under the action of the angle spring 306, the othersensing lever havg meanwhile arrived at the initial position. The lattersensing lever then engages the mirror whereas the former sensing leverturns slowly back to the initial position. Large inertial. forces arethus avoided in connection with which the fact that the cams 313, 314are arranged on the shaft 301 of the sprocket wheel 302 which is drivenin. synchronism with the film, ensures synchronous motion of the cammingprofiles and the film. 1

In order to ensure the alternate engagement of the pawls 325, 326 on themirror,-the pawl carries 315, 316 are respectively provided with controllevers 327, 328. The control levers 327, 328 are turnable about a pivotshaft 329. Control cams 330, 331 are provided to control the movementsof the control levers 327, 328 which ride on such control cam profile,respectively, as shown in FIG. 26. The control cams 330, 331 aredisplaced a half division from one another in similar manner to the cams313, 314.

At one side the control levers 327, 328 lie on the control cams 330, 331and on the other side on the pawl carrie 315, 316. Projecting cammingsurfaces on the control cam 330, 331 respectively produce an angularmovement of respective control levers in the counter clockwise directionto displace the associated pawl carriers 315, 316 together with theirrespective elongated slots 317, 318 in relation to the axle pin 304.

With counterclockwise movement of one or other of the control levers327, 328 displacement of the associated pawl carrier 315, 316 occursupwardly (as shown with pawl carrier 315 in FIG. 26) against the forceof its respective tension spring 319, 320 thereby advancing the time ofdisengagement of the respective pawls 325, 326 with the mirror 303. Themirror 303 is then turned in the counterclockwise direction under theaction of the angle spring 306 and brought back to its original positionin which it is operatively engaged by the pawl of the other pawlcarrier. The tilt-mirror 303 then executes a fresh pivoting motion underthe action of this latter pawl.

In order to avoid vibration of the mirror with engagement of the pawls325, 326 the pawls are suitably provided with a springy portion of thesame mass as the tilt-mirror 303. At the moment of impact of thetiltmirror 303 on this springy portion, the movement is transferred fromthe mirror 303 to the springy portion in accordance with the laws ofelastic impact in such a way as to enable the mirror to be moved by theindividual pawls without further oscillatory movement. To at-. tain thisresult, namely absorbing the kinetic energy of the mirror in such a waythat there is no bounce when it strikes the pawl, it may be expeditiousto arrange for controllable adjustment of the pawls 325, 326 and/or theabuttment of the control levers 327, 328 on the control cams 330, 331and/or on the pawl carriers 315, 316.

FIG. 30 shows an arrangement in which the mirror 303 is controlled bytraction claws 332, 333 instead of by cams. These traction claws 332,333 are mounted on pivots 336, 337 provided on claw levers 334, 335 andare spring loaded by angle springs 338, 339. The claw levers 334, 335are mounted on a common axis 340 which is arranged eccentrically to theaxis of the tiltmirror 303. Each of the claw levers 334, 335 has arespective pawl 341, 342 for the tilt-mirror 303. The pawls 341, 342 aresecured in adjustable manner in elongated slots 343, 344 provided on theclaw levers 334, 335. Each of the pawls 341, 342 is mounted on arespective springy strip 345, 346 and is provided on its leading endwith a respective ramp surface 347, 348.

The claw lever 335 is provided with a cranked end i 349 with which itcan engage from one side behind a film 1 travelling across a film gate350, so that the claw lever 333 co-operates with the same row of filmperforations as the claw lever 332. t

In the same way as in the previously described example (FIG. 24) thealternately operating traction claws provide the drive for thetilt-mirror 303 starting from the initial position illustrated in FIG.30, the tilt-mirror 303 is moved by the pawl 341 in unison with thetransport of the film 1 in the direction of the arrow 352 as a result ofthe traction of the claw 332 engaged in one of the perforations of thefilm. As the claw levers 334,

305, there is a point of intersection between the movements at the radiiof the tilt-mirror and the two pawls 341, 342 respectively. The mirror303 is automatically released from its operating pawl at thisintersection point and returns under the influence of a restoring spring306a to the initial position. The operating claw levers 334 and 335respectively continue to participate in the movement of the film untilstops 353, 354, which are positionally fixed but which if necessary canbe adjustable,. strike against respective arms of the angleshapedtraction claws 332, 333 whereupon the traction claw is extracted fromthe perforation of the film. The

operating claw lever-then returns either under its own weight or underthe influence of an unillustrated spring to an initial positiondetermined by a further stop 355. During this return motion the claw inquestion which in the arrangement illustrated in FIG. 30 would next bethe traction claw 333 slides along the perforated margin of the film.The traction claw 333 would then fall in the next operating perforationunder the influence of the angle spring 339. However this'perforation isoccupied by the other traction claw 332. For this reason the claw 333 infact arrives at the initial position determined by the stop 355 which,if necessary, is adjustable. During themovement of the traction claw 333and its claw lever 335, the pawl 342 strikes the edge of the tilt-mirrorwith its ramp surface 348 which is resiliently deflected thereby so asto engage once again behind the mirror 303. As the forces absorbed bythe pawls 341, 342 are, comparatively speaking, negligible, the bendingmoments exercised by the spring strips 345, 346 can also becomparatively small.

We claim: 1. Film handling apparatus for a film comprising a film gatedefining a window, drive means continuously operable to continuouslythrough said film gate, optical means defining an optical path extendingto said window, a deflector in said optical path, an axis about whichsaid deflector is rockable, deflector drive means operable in onedirection to produce a forward motion of said deflector and operable inthe reverse direction to produce an accelerated return motion of saiddeflector, an electrical pulse-generating circuit controlling operationof said deflector drive means, an arrangement synchronizing theapplication of said pulse generating circuit on said deflector drivedrive said film means with movement of said film through said film gate,and

an electrical energy transfer means in said pulse-, generating circuitand co-operating with said drive means at the end of said return motionof said deflector for transferring to said deflector a predeterminedpulse of energy equal to the dynamic energy of the deflector such thatthe return motion of the deflector is abruptly halted without recoilwhen it is at a chosen position corresponding to completion .of saidreturn motion,

said electrical pulse generating circuit and synchronizing arrangementincluding:

a phase comparator,

means for amplifying synchronizing impulses derived from perforations ofsaid film, and said amplifying means connected to said phase comparator,

a saw tooth generator

1. Film handling apparatus for a film comprising a film gate defining awindow, drive means continuously operable to drive said filmcontinuously through said film gate, optical means defining an opticalpath extending to said window, a deflector in said optical path, an axisabout which said deflector is rockable, deflector drive means operablein one direction to produce a forward motion of said deflector andoperable in the reverse direction to produce an accelerated returnmotion of said deflector, an electrical pulse-generating circuitcontrolling operation of said deflector drive means, an arrangementsynchronizing the application of said pulse generating circuit on saiddeflector drive means with movement of saiD film through said film gate,and an electrical energy transfer means in said pulse-generating circuitand co-operating with said drive means at the end of said return motionof said deflector for transferring to said deflector a predeterminedpulse of energy equal to the dynamic energy of the deflector such thatthe return motion of the deflector is abruptly halted without recoilwhen it is at a chosen position corresponding to completion of saidreturn motion, said electrical pulse generating circuit andsynchronizing arrangement including: a phase comparator, means foramplifying synchronizing impulses derived from perforations of saidfilm, and said amplifying means connected to said phase comparator, asaw tooth generator a double impulse generator, an oscillator connectedto said phase comparator such that the frequency of said oscillator iscompared in said phase comparator and controls said oscillator so thatthe frequency and phase of the oscillator output and the synchronizingimpulses coincide, and said oscillator output is connected to said sawtooth generator and to said double impulse generator, a mixing circuitconnected to the outputs of said saw tooth generator and said doubleimpulse generator, respectively said deflector drive means including amotor, and an output stage connected between said mixing circuit andsaid motor.
 2. The apparatus, as set forth in claim 1, wherein saidpulse generating circuit provides a wave-form to said deflector drivemeans comprising a sawtooth-shaped first pulse part driving saiddeflector forwardly, an oppositely directed second pulse part drivingsaid deflector rearwardly, and a third pulse part providing saidpredetermined pulse of energy to halt the deflector return motion.